ncap(1) netCDF Arithmetic Processor


ncap [-3] [-4] [-6] [-7] [-A] [-C] [-c] [-D dbg_lvl] [-F] [-f] [--glb att_name= att_val]] [-h] [--hdf] [--hdr_pad sz] [-L dfl_lvl] [-l path] [--no_tmp_fl] [-O] [-o output-file] [-p path] [-R] [-r] [--ram_all] [-S script-file][-s script][-v var[, ... ]] input-file [ output-file ]


ncap arithmetically processes a netCDF file. However, in about 2008 ncap was deprecated in favor of ncap2 which far surpasses its capabilities. ncap will eventually be completely removed from NCO. It is currently retained only because it provides an easier-to-build arithmetic operator than ncap2.

The processing instructions are contained either in the NCO script file fl.nco or in a sequence of command line arguments. The options -s (or long options --spt or --script) are used for in-line scripts and -S (or long options --fl_spt or --script-file) are used to provide the filename where (usually multiple) scripting commands are pre-stored. ncap was written to perform arbitrary albebraic transformations of data and archive the results as easily as possible. Missing values are treated correctly. The results of the algebraic manipulations are called derived fields.

Unlike the other operators, ncap does not accept a list of variables to be operated on as an argument to -v. Rather, the -v switch takes no arguments and indicates that ncap should output only user-defined variables. ncap does not accept or understand the -x switch.


Compute the square of variable T

ncap -s "T2=T*T"


NCO manual pages written by Charlie Zender and originally formatted by Brian Mays.


Report bugs to <>.


Copyright © 1995-2016 Charlie Zender
This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.


The NCO homepage at <> contains more information.